the former situation, the nets (18.2 m x 1.3 m) are 

 stretched between bamboo poles stuck to the bot- 

 tom, with the nets being tied at the mean water level. 

 The nets with P. pseudolineciris growing on them 

 float on the water surface, anchored to maintain their 

 position, and kept on the surface by glass or plastic 

 floats. 



Recent work by Imada and co-workers has 

 yielded results that could increase the production of 

 nori. This research indicated that amino acids are 

 effective growth promoting substances for Porphym 

 and that the exposure of the fronds to air by tidal 

 fluctuations is a significant factor in disease control 

 (Imada, Saito. and Teramoto, 1971). Crossing ex- 

 periments by Suto between different species of cul- 

 tivated Porpliyra succeeded, the cross developing 

 to the Conchocelis phase. Other attempts at cross- 

 ing monoecious and dioecious species, and between 

 species with different chromosome numbers were 

 not as successful (Suto, 1971). 



Production and Use 



The demand for nori in Japan and the increasing 

 production capability have resulted in a very sig- 

 nificant industry. In 1970. about 60,000 hectares 

 (150,000 acres) of coastal waters in Japan were 

 being used for nori cultivation. This acreage pro- 

 duced nearly 6 billion sheets of the dried product 

 worth 70-80 billion yen per year (approximately 

 $230 million). Each paper-thin sheet is 20 cm (8 in- 

 ches square and weighs about 3 g. In addition, 200 

 million sheets are imported from Korea, a number 

 now limited by an import restriction and one which 

 could be increased to I billion sheets in the future 

 (see Suto). 



Approximately 60,000 fisheiTnen are now cultivat- 

 ing nori. setting about 10 million nets each year and 

 realizing the 509f (Furukawa, 1971) to 70% (see 

 Suto) net income for their efforts. This level of pro- 

 duction is required to meet the needs of the average 

 Japanese who consumes 50-60 sheets of nori per 

 year. The price of nori, up to $15 per kilogram dry 

 weight (nearly $7 per pound), is a major factor in 

 making this the most profitable of all fisheries in 

 Japan. 



Problems and Needed .Advances 



In spite of the high level of productivity, the 

 Japanese recognize the need to increase their pro- 

 duction and improve the profit potential of this 



fishery. Briefly summarized, these problems and ac- 

 tivities are as follows. (Again, see Suto's paper in 

 this report for a more complete description of them. ) 



1. Development of new nori grounds or improve- 

 ment of old ones, using the new net collector 

 techniques, the floating net cultures and coastal 

 engineering works (pilings to protect growing 

 areas, deepening such areas to increase water 

 exchange, etc.). This would bring new areas into 

 production to replace old ones lost because of 

 pollution and increase the productivity of existing 

 areas. 



2. Prevention of large-scale fluctuations (heavy 

 losses) yearly production primarily through dis- 

 ease control. This is done partially now by pre- 

 venting overcrowding of the nets in the growing 

 areas and by refrigerating the "buds'" (juvenile 

 plants, 5-50 mm in length) at -20°C. This re- 

 frigerating procedure is applied to a large part of 

 the newly hatched fronds essentially for the pro- 

 curement of frond stocks. These stocks are used 

 to replace poorer quality fronds in the growing 

 areas. By refrigerating these buds, the '"weeds" 

 (such as Enteromorpha) and diatoms are killed, 

 and the development of a parasitic fungus is pre- 

 vented. By 1970, one-half of all culture nets used 

 were refrigerated using this technique (Okazaki, 

 1971). Most of the diseases or diseaselike prob- 

 lems are not well understood, or. in many in- 

 stances, not even identified. Frequently, the 

 plants appear to be infected by a fungus, but this 

 could be caused by environmental or physiologi- 

 cal conditions (temperature, salinity, malnutri- 

 tion, etc.). Most of these conditions are called 

 various kinds and colors of "spot disease" or 

 "rots," but the exact causitive agent is not iden- 

 tified. 



Work reported recently by Ishio and his co- 

 workers identified pollution from chemical plants 

 as a cause of one type of algal disease. A "can- 

 cerous"" disease observed in Porpliyra in shallow 

 coastal waters polluted by industrial wastes was 

 shown to be related to contact between the fronds 

 and the contaminated bottom mud. The mud was 

 extracted and it was found that the carcinogenic 

 fraction contained a mixture of organic com- 

 pounds discharged by a dye factor) which uses tar 

 distillates as raw materials (Ishio. Yano. and 

 Nakagawa. 1972). 



3. Mechanization of nori cultivation and processing. 

 With the current labor shortage in Japan and other 



98 



